Optimization of a cisplatin model of chemotherapy-induced peripheral neuropathy in mice: use of vitamin C and sodium bicarbonate pretreatments to reduce nephrotoxicity and improve animal health status

Membrane Association of the Short Transglutaminase Type 2 Splice Variant (TG2-S) Modulates Cisplatin Resistance in a Human Hepatocellular Carcinoma (HepG2) Cell Line

Hepatocellular carcinoma (HCC) is a heterogeneous malignancy with complex carcinogenesis. Although there has been significant progress in the treatment of HCC over the past decades, drug resistance to chemotherapy remains a major obstacle in its successful management. In this study, we were able to reduce chemoresistance in cisplatin-resistant HepG2 cells by either silencing the expression of transglutaminase type 2 (TG2) using siRNA or by the pre-treatment of cells with the TG2 enzyme inhibitor cystamine. Further analysis revealed that, whereas the full-length TG2 isoform (TG2-L) was almost completely cytoplasmic in its distribution, the majority of the short TG2 isoform (TG2-S) was membrane-associated in both parental and chemoresistant HepG2 cells. Following the induction of cisplatin toxicity in non-chemoresistant parental cells, TG2-S, together with cisplatin, quickly relocated to the cytosolic fraction. Conversely, no cytosolic relocalisation of TG2-S or nuclear accumulation cisplatin was observed, following the identical treatment of chemoresistant cells, where TG2-S remained predominantly membrane-associated. This suggests that the deficient subcellular relocalisation of TG2-S from membranous structures into the cytoplasm may limit the apoptic response to cisplatin toxicity in chemoresistant cells. Structural analysis of TG2 revealed the presence of binding motifs for interaction of TG2-S with the membrane scaffold protein LC3/LC3 homologue that could contribute to a novel mechanism of chemotherapeutic resistance in HepG2 cells.

Assessing Dose- and Sex-Dependent Antinociceptive Effects of Cannabidiol and Amitriptyline, Alone and in Combination, and Exploring Mechanism of Action Involving Serotonin 1A Receptors

Inflammatory pain is caused by tissue hypersensitization and is a component of rheumatic diseases, frequently causing chronic pain. Current guidelines use a multimodal approach to pain and sociocultural changes have renewed interest in cannabinoid use, particularly cannabidiol (CBD), for pain. The tricyclic antidepressant amitriptyline (AT) is approved for use in pain-related syndromes, alone and within a multimodal approach. Therefore, we investigated sex- and dose-dependent effects of CBD and AT antinociception in the 2.5% formalin inflammatory pain model. Male and female C57BL/6J mice were pretreated with either vehicle, CBD (0.3-100 mg/kg), or AT (0.1-30 mg/kg) prior to formalin testing. In the acute phase, CBD induced antinociception after administration of 30-100 mg/kg in males and 100 mg/kg in females and in the inflammatory phase at doses of 2.5-100 mg/kg in males and 10-100 mg/kg in females. In the acute phase, AT induced antinociception at 10 mg/kg for all mice, and at 0.3 mg/kg in males and 3 mg/kg in female mice in the inflammatory phase. Combining the calculated median effective doses of CBD and AT produced additive effects for all mice in the acute phase and for males only in the inflammatory phase. Use of selective serotonin 1A receptor antagonist N-[2-[4-(2-methoxyphenyl)-1 piperazinyl]ethyl]-N-2-pyridinylcyclohexanecarboxamide (WAY-100635) maleate (0.1 mg/kg) before co-administration of CBD and AT reversed antinociception in the acute and partially reversed antinociception in the inflammatory phase. Administration of AT was found to enhance cannabinoid receptor type 1mRNA expression only in female mice. These results suggest a role for serotonin and sex in mediating cannabidiol and amitriptyline-induced antinociception in inflammatory pain. SIGNIFICANCE STATEMENT: Inflammatory pain is an important component of both acute and chronic pain. We have found that cannabidiol (CBD) and amitriptyline (AT) show dose-dependent, and that AT additionally shows sex-dependent, antinociceptive effects in an inflammatory pain model. Additionally, the combination of CBD and AT was found to have enhanced antinociceptive effects that is partially reliant of serotonin 1A receptors and supports the use of CBD within a multimodal approach to pain.

Antinociceptive Effects of Cannabichromene (CBC) in Mice: Insights from von Frey, Tail-Flick, Formalin, and Acetone Tests

Cannabis sativa contains minor cannabinoids that have potential therapeutic value in pain management. However, detailed experimental evidence for the antinociceptive effects of many of these minor cannabinoids remains lacking. Here, we employed artificial intelligence (AI) to perform compound-protein interaction estimates with cannabichromene (CBC) and receptors involved in nociceptive signaling. Based on our findings, we investigated the antinociceptive properties of CBC in naïve or neuropathic C57BL/6 male and female mice using von Frey (mechanical allodynia), tail-flick (noxious radiant heat), formalin (acute and persistent inflammatory pain), and acetone (cold thermal) tests. For von Frey assessments, CBC dose (0-20 mg/kg, i.p.) and time (0-6 h) responses were measured in male and female neuropathic mice. For tail-flick, formalin, and acetone assays, CBC (20 mg/kg, i.p.) was administered to naïve male and female mice 1 h prior to testing. The results show that CBC (10 and 20 mg/kg, i.p.) significantly reduced mechanical allodynia in neuropathic male and female mice 1-2 h after treatment. Additionally, CBC treatment caused significant reductions in nociceptive behaviors in the tail-flick assay and in both phase 1 and phase 2 of the formalin test. Finally, we found a significant interaction in neuropathic male mice in the acetone test. In conclusion, our results suggest that CBC targets receptors involved in nociceptive signaling and imparts antinociceptive properties that may benefit males and females afflicted with diverse forms of acute or chronic/persistent pain.

Chronic Cannabigerol as an Effective Therapeutic for Cisplatin-Induced Neuropathic Pain

Cannabigerol (CBG), derived from the cannabis plant, acts as an acute analgesic in a model of cisplatin-induced peripheral neuropathy (CIPN) in mice. There are no curative, long-lasting treatments for CIPN available to humans. We investigated the ability of chronic CBG to alleviate mechanical hypersensitivity due to CIPN in mice by measuring responses to 7 and 14 days of daily CBG. We found that CBG treatment (i.p.) for 7 and 14 consecutive days significantly reduced mechanical hypersensitivity in male and female mice with CIPN and reduced pain sensitivity up to 60-70% of baseline levels (p < 0.001 for all), 24 h after the last injection. Additionally, we found that daily treatment with CBG did not evoke tolerance and did not incur significant weight change or adverse events. The efficacy of CBG was independent of the estrous cycle phase. Therefore, chronic CBG administration can provide at least 24 h of antinociceptive effect in mice. These findings support the study of CBG as a long-lasting neuropathic pain therapy, which acts without tolerance in both males and females.

Kinin B2 Receptor Mediates Cisplatin-Induced Painful Peripheral Neuropathy by Intracellular Kinase Pathways and TRPA1 Channel Sensitisation

Chemotherapy-induced peripheral neuropathy is a severe clinical problem frequently associated with cisplatin use. Although its pathophysiology is poorly understood, it is known that kinin receptors and the transient receptor potential ankyrin 1 (TRPA1) channel play a significant role in the peripheral neuropathy induced by cisplatin in rodents. However, the role of signalling pathways downstream from B₂ kinin receptors activation and sensitisation of the TRPA1 channel remains unknown in this model. The cisplatin-induced neuropathy model caused mechanical and cold allodynia in male Swiss mice. Antagonists for kinin B₂ and B₁ receptors and the TRPA1 channel attenuated the painful parameters. Local sub-nociceptive doses of kinin B₂ receptor (bradykinin) and TRPA1 channel (allyl isothiocyanate; AITC) agonists enhanced the painful parameters in cisplatin-treated mice, which their respective antagonists attenuated. Furthermore, we demonstrated the interaction between the kinin B₂ receptor and the TRPA1 channel in cisplatin-induced peripheral neuropathy since phospholipase C (PLC) and protein kinase C epsilon (PKCε) inhibitors attenuated the increase in mechanical and cold allodynia evoked by bradykinin and AITC in cisplatin-treated mice. Therefore, regulating the activation of signalling pathways downstream from the kinin B₂ receptors activation and TRPA1 channel sensitisation can mitigate the painful peripheral neuropathy decurrent of the oncology treatment with cisplatin.

CaMKII and CaV3.2 T-type calcium channel mediate Connexin-43-dependent inflammation by activating astrocytes in vincristine-induced neuropathic pain

Vincristine (VCR), an alkaloid isolated from vinca, is a commonly used chemotherapeutic drug. However, VCR therapy can lead to dose-dependent peripheral neurotoxicity, mainly manifesting as neuropathic pain, which is one of the dominant reasons for limiting its utility. Experimentally, we discovered that VCR-induced neuropathic pain (VINP) was accompanied by astrocyte activation; the upregulation of phospho-CaMKII (p-CaMKII), CaV3.2, and Connexin-43 (Cx43) expression; and the production and release of inflammatory cytokines and chemokines in the spinal cord. Similar situations were also observed in astrocyte cultures. Interestingly, these alterations were all reversed by intrathecal injection of KN-93 (a CaMKII inhibitor) or L-Ascorbic acid (a CaV3.2 inhibitor). In addition, KN-93 and L-Ascorbic acid inhibited the increase in [Ca2+]i associated with astrocyte activation. We also verified that knocking down or inhibiting Cx43 level via intrathecal injection of Cx43 siRNA or Gap27 (a Cx43 mimetic peptide) relieved pain hypersensitivity and reduced the release of inflammatory factors; however, they did not affect astrocyte activation or p-CaMKII and CaV3.2 expression. Besides, the overexpression of Cx43 through the transfection of the Cx43 plasmid did not affect p-CaMKII and CaV3.2 expressions in vitro. Therefore, CaMKII and CaV3.2 may activate astrocytes by increasing [Ca2+]i, thereby mediating Cx43-dependent inflammation in VINP. Moreover, we demonstrated that the CaMKII signalling pathway was involved in VCR-induced inflammation, apoptosis, and mitochondrial damage. Collectively, our findings show a novel mechanism by which CaMKII and CaV3.2 mediate Cx43-dependent inflammation by activating astrocytes in neuropathic pain induced by VCR.

Kinin B1 and B2 Receptors Contribute to Cisplatin-Induced Painful Peripheral Neuropathy in Male Mice

Cisplatin is the preferential chemotherapeutic drug for highly prevalent solid tumours. However, its clinical efficacy is frequently limited due to neurotoxic effects such as peripheral neuropathy. Chemotherapy-induced peripheral neuropathy is a dose-dependent adverse condition that negatively impacts quality of life, and it may determine dosage limitations or even cancer treatment cessation. Thus, it is urgently necessary to identify pathophysiological mechanisms underlying these painful symptoms. As kinins and their B1 and B2 receptors contribute to the development of chronic painful conditions, including those induced by chemotherapy, the contribution of these receptors to cisplatin-induced peripheral neuropathy was evaluated via pharmacological antagonism and genetic manipulation in male Swiss mice. Cisplatin causes painful symptoms and impaired working and spatial memory. Kinin B1 (DALBK) and B2 (Icatibant) receptor antagonists attenuated some painful parameters. Local administration of kinin B1 and B2 receptor agonists (in sub-nociceptive doses) intensified the cisplatin-induced mechanical nociception attenuated by DALBK and Icatibant, respectively. In addition, antisense oligonucleotides to kinin B1 and B2 receptors reduced cisplatin-induced mechanical allodynia. Thus, kinin B1 and B2 receptors appear to be potential targets for the treatment of cisplatin-induced painful symptoms and may improve patients’ adherence to treatment and their quality of life.

The Therapeutic Potential of Antioxidants in Chemotherapy-Induced Peripheral Neuropathy: Evidence from Preclinical and Clinical Studies

As cancer therapies advance and patient survival improves, there has been growing concern about the long-term adverse effects that patients may experience following treatment, and concerns have been raised about such persistent, progressive, and often irreversible adverse effects. Chemotherapy is a potentially life-extending treatment, and chemotherapy-induced peripheral neuropathy (CIPN) is one of its most common long-term toxicities. At present, strategies for the prevention and treatment of CIPN are still an open problem faced by medicine, and there has been a large amount of previous evidence that oxidative damage is involved in the process of CIPN. In this review, we focus on the lines of defense involving antioxidants that exert the effect of inhibiting CIPN. We also provide an update on the targets and clinical prospects of different antioxidants (melatonin, N-acetylcysteine, vitamins, α-lipoic acid, mineral elements, phytochemicals, nutritional antioxidants, cytoprotectants and synthetic compounds) in the treatment of CIPN with the help of preclinical and clinical studies, emphasizing the great potential of antioxidants as adjuvant strategies to mitigate CIPN.

Efficient Synthesis for Altering Side Chain Length on Cannabinoid Molecules and Their Effects in Chemotherapy and Chemotherapeutic Induced Neuropathic Pain

(1) Background: Recently, a number of side chain length variants for tetrahydrocannabinol and cannabidiol have been identified in cannabis; however, the precursor to these molecules would be based upon cannabigerol (CBG). Because CBG, and its side chain variants, are rapidly converted to other cannabinoids in the plant, there are typically only small amounts in plant extracts, thus prohibiting investigations related to CBG and CBG variant therapeutic effects. (2) Methods: To overcome this, we developed an efficient synthesis of corresponding resorcinol fragments using the Wittig reaction which, under acid catalyzed coupling with geraniol, produced the desired side chain variants of CBG. These compounds were then tested in an animal model of chemotherapeutic-induced neuropathic pain and to reduce colorectal cancer cell viability. (3) Results: We found that all side-chain variants were similarly capable of reducing neuropathic pain in mice at a dose of 10 mg/kg. However, the molecules with shorter side chains (i.e., CBGV and CBGB) were better at reducing colorectal cancer cell viability. (4) Conclusions: The novel synthesis method developed here will be of utility for studying other side chain derivatives of minor cannabinoids such as cannabichromene, cannabinol, and cannabielsoin.

Combinations of Cannabidiol and Δ9-Tetrahydrocannabinol in Reducing Chemotherapeutic Induced Neuropathic Pain

Neuropathic pain is a condition that impacts a substantial portion of the population and is expected to affect a larger percentage in the future. This type of pain is poorly managed by current therapies, including opioids and NSAIDS, and novel approaches are needed. We used a cisplatin-induced model of neuropathic pain in mice to assess the effects of the cannabinoids THC and CBD alone or in varying ratios as anti-nociceptive agents. In addition to testing pure compounds, we also tested extracts containing high THC or CBD at the same ratios. We found that pure CBD had little impact on mechanical hypersensitivity, whereas THC reduced mechanical hypersensitivity in both male and female mice (as has been reported in the literature). Interestingly, we found that high CBD cannabis extract, at the same CBD dose as pure CBD, was able to reduce mechanical hypersensitivity, although not to the same level as high THC extract. These data suggest that, at least for CBD-dominant cannabis extracts, there is an increase in the anti-nociceptive activity that may be attributed to other constitutes of the plant. We also found that high THC extract or pure THC is the most efficacious treatment for reducing neuropathic pain in this model.

Cannabigerol (CBG) attenuates mechanical hypersensitivity elicited by chemotherapy-induced peripheral neuropathy

BACKGROUND

Cannabigerol (CBG) is a non-psychoactive phytocannabinoid produced by the plant Cannabis sativa with affinity to various receptors involved in nociception. As a result, CBG is marketed as an over-the-counter treatment for many forms of pain. However, there is very little research-based evidence for the efficacy of CBG as an anti-nociceptive agent.

METHODS

To begin to fill this knowledge gap, we assessed the anti-nociceptive effects of CBG in C57BL/6 mice using three different models of pain; cisplatin-induced peripheral neuropathy, the formalin test, and the tail-flick assay.

RESULTS

Using the von Frey test, we found that CBG-attenuated mechanical hypersensitivity evoked by cisplatin-induced peripheral neuropathy in both male and female mice. Additionally, we observed that this CBG-induced reduction in mechanical hypersensitivity was attenuated by the α₂ -adrenergic receptor antagonist atipamezole (3 mg/kg, i.p.) and the CB₁ R antagonist, AM4113 (3 mg/kg, i.p.), and blocked by the CB₂ R antagonist/inverse agonist, SR144528 (10 mg/kg, i.p.). We found that the TRPV1 antagonist, SB705498 (20 mg/kg, i.p.) was unable to prevent CBG actions. Furthermore, we show that CBG:CBD oil (10 mg/kg, i.p.) was more effective than pure CBG (10 mg/kg) at reducing mechanical hypersensitivity in neuropathic mice. Lastly, we show that pure CBG and CBG:CBD oil were ineffective at reducing nociception in other models of pain, including the formalin and tail flick assays.

CONCLUSIONS

Our findings support the role of CBG in alleviating mechanical hypersensitivity evoked by cisplatin-induced peripheral neuropathy, but highlight that these effects may be limited to specific types of pain.

SIGNIFICANCE

There are few effective treatments for neuropathic pain and neuropathic pain is projected to increase with the aging population. We demonstrate that CBG (cannabigerol) and CBG:CBD oil attenuate neuropathy-induced mechanical hypersensitivity mice. Second, we identify receptor targets that mediate CBG-induced reduction in mechanical hypersensitivity in neuropathic mice. Third, we demonstrate that an acute injection of CBG is anti-nociceptive specifically for neuropathic pain rather than other forms of pain, including persistent pain and thermal pain.

Decursinol-mediated antinociception and anti-allodynia in acute and neuropathic pain models in male mice: Tolerance and receptor profiling

Korean scientists have shown that oral administration of Angelica gigas Nakai (AGN) root alcoholic extract and the metabolite of its pyranocoumarins, decursinol, have antinociceptive properties across various thermal and acute inflammatory pain models. The objectives of this study were 1) to assess whether tolerance develops to the antinociceptive effects of once-daily intraperitoneally administered decursinol (50 mg/kg) in acute thermal pain models, 2) to establish its anti-allodynic efficacy and potential tolerance development in a model of chemotherapy-evoked neuropathic pain (CENP) and 3) to probe the involvement of select receptors in mediating the pain-relieving effects with antagonists. The results show that decursinol induced antinociception in both the hot plate and tail-flick assays and reversed mechanical allodynia in mice with cisplatin-evoked neuropathic pain. Tolerance was detected to the antinociceptive effects of decursinol in the hot plate and tail-flick assays and to the anti-allodynic effects of decursinol in neuropathic mice. Pretreatment with either the 5-HT2 antagonist methysergide, the 5-HT2A antagonist volinanserin, or the 5-HT2C antagonist SB-242084 failed to attenuate decursinol-induced antinociception in the tail-flick assay. While pretreatment with the cannabinoid inverse agonists rimonabant and SR144528 failed to modify decursinol-induced anti-allodynia, pretreatment with the opioid antagonist naloxone partially attenuated the anti-allodynic effects of decursinol. In conclusion, our data support decursinol as an active phytochemical of AGN having both antinociceptive and anti-allodynic properties. Future work warrants a more critical investigation of potential receptor mechanisms as they are likely more complicated than initially reported.

A Panax quinquefolius-Based Preparation Prevents the Impact of 5-FU on Activity/Exploration Behaviors and Not on Cognitive Functions Mitigating Gut Microbiota and Inflammation in Mice

Simple Summary

Chemotherapy-related cognitive impairment (CRCI) and fatigue worsen the quality of life (QoL) of cancer patients. Multicenter studies have shown that Panax quinquefolius and vitamin C, respectively, were effective in reducing the symptoms of fatigue in treated cancer patients. We developed a behavioral C57Bl/6j mouse model to study the impact of 5-Fluorouracil (5-FU) chemotherapy on activity/fatigue, emotional reactivity and cognitive functions. We used this model to evaluate the potentially beneficial role of a Panax quinquefolius-based solution containing vitamin C (Qiseng^®) or vitamin C alone in these chemotherapy side effects. We established that Qiseng^® prevents the reduction in activity/exploration and symptoms of fatigue induced by 5-FU and dampens chemotherapy-induced intestinal dysbiosis and systemic inflammation. We further showed that Qiseng^® decreases macrophage infiltration in the intestinal compartment, thus preventing, at least in part, the systemic elevation of IL-6 and MCP-1 and further reducing the neuroinflammation likely responsible for the fatigue induced by chemotherapy, a major advance toward improving the QoL of patients.

Abstract

Chemotherapy-related cognitive impairment (CRCI) and fatigue constitute common complaints among cancer patient survivors. Panax quinquefolius has been shown to be effective against fatigue in treated cancer patients. We developed a behavioral C57Bl/6j mouse model to study the role of a Panax quinquefolius-based solution containing vitamin C (Qiseng^®) or vitamin C alone in activity/fatigue, emotional reactivity and cognitive functions impacted by 5-Fluorouracil (5-FU) chemotherapy. 5-FU significantly reduces the locomotor/exploration activity potentially associated with fatigue, evokes spatial cognitive impairments and leads to a decreased neurogenesis within the hippocampus (Hp). Qiseng^® fully prevents the impact of chemotherapy on activity/fatigue and on neurogenesis, specifically in the ventral Hp. We observed that the chemotherapy treatment induces intestinal damage and inflammation associated with increased levels of Lactobacilli in mouse gut microbiota and increased expression of plasma pro-inflammatory cytokines, notably IL-6 and MCP-1. We demonstrated that Qiseng^® prevents the 5-FU-induced increase in Lactobacilli levels and further compensates the 5-FU-induced cytokine release. Concomitantly, in the brains of 5-FU-treated mice, Qiseng^® partially attenuates the IL-6 receptor gp130 expression associated with a decreased proliferation of neural stem cells in the Hp. In conclusion, Qiseng^® prevents the symptoms of fatigue, reduced chemotherapy-induced neuroinflammation and altered neurogenesis, while regulating the mouse gut microbiota composition, thus protecting against intestinal and systemic inflammation.

Protective effect of food derived nutrients on cisplatin nephrotoxicity and its mechanism

Platinum-based metal complexes, especially cisplatin (cis-diamminedichloroplatinum II, CDDP), possess strong anticancer properties and a broad anticancer spectrum. However, the clinical application of CDDP has been limited by its side effects including nephrotoxicity, ototoxicity, and neurotoxicity. Furthermore, the therapeutic effects of current clinical protocols are imperfect. Accordingly, it is essential to identify key targets and effective clinical protocols to restrict CDDP-induced nephrotoxicity. Herein, we first analyzed the relevant molecular mechanisms during the process of CDDP-induced nephrotoxicity including oxidative stress, apoptosis, and inflammation. Evidence from current studies was collected and potential targets and clinical protocols are summarized. The evidence indicates an efficacious role of nutrition-based substances in CDDP-induced renal injury.

A Novel Plant-Derived Choline Transporter-like Protein 1 Inhibitor, Amb544925, Induces Apoptotic Cell Death via the Ceramide/Survivin Pathway in Tongue Squamous Cell Carcinoma

BACKGROUND

Despite recent advances in the early detection and treatment of TSCC patients, recurrence rates and survival rates have not improved. The high frequency of lymph node metastasis is one of the causes, and the drug development of new therapeutic mechanisms such as metastasis control is desired. Choline transporter-like protein 1 (CTL1) has attracted attention as a target molecule in cancer therapy. In this study, we examined the antitumor effects of Amb544925, a plant-derived CTL1 inhibitor.

METHODS

The TSCC cell line HSC-3 was used to measure [3H]choline uptake, cell survival, caspase activity, and cell migration. Xenograft model mice were prepared to verify the antitumor effect of Amb544925.

RESULTS

Amb544925 inhibited cell viability and increased caspase-3/7 activity at concentrations that inhibited choline uptake. Amb544925 and ceramide increased SMPD4 expression and suppressed surivivin expression. Furthermore, Amb544925 and ceramide inhibited the migration of HSC-3 cells. In the xenograft model mice, Amb544925 suppressed tumor growth and CTL1 mRNA expression.

CONCLUSIONS

The plant-derived CTL1 inhibitor Amb544925 is a lead compound of a new anticancer agent exhibiting antitumor effects and inhibition of cell migration through the ceramide/survivin pathway.

Cisplatin Mouse Models: Treatment, Toxicity and Translatability

Cisplatin is one of the most widely used chemotherapeutic drugs in the treatment of a wide range of pediatric and adult malignances. However, it has various side effects which limit its use. Cisplatin mouse models are widely used in studies investigating cisplatin therapeutic and toxic effects. However, despite numerous promising results, no significant improvement in treatment outcome has been achieved in humans. There are many drawbacks in the currently used cisplatin protocols in mice. In the paper, the most characterized cisplatin protocols are summarized together with weaknesses that need to be improved in future studies, including hydration and supportive care. As demonstrated, mice respond to cisplatin treatment in similar ways to humans. The paper thus aims to illustrate the complexity of cisplatin side effects (nephrotoxicity, gastrointestinal toxicity, neurotoxicity, ototoxicity and myelotoxicity) and the interconnectedness and interdependence of pathomechanisms among tissues and organs in a dose- and time-dependent manner. The paper offers knowledge that can help design future studies more efficiently and interpret study outcomes more critically. If we want to understand molecular mechanisms and find therapeutic agents that would have a potential benefit in clinics, we need to change our approach and start to treat animals as patients and not as tools.

Sex and dose-dependent antinociceptive effects of the JNK (c-Jun N-terminal kinase) inhibitor SU 3327 are mediated by CB2 receptors in female, and CB1/CB2 receptors in male mice in an inflammatory pain model

Activation of c-Jun N-terminal kinases (JNKs) has been implicated in the development and persistence of inflammatory and neuropathic pain in animal models. Moreover, JNKs have been involved in the maintenance of chronic pain, as well as development of tolerance to antinociceptive agents in the opioid and cannabinoid class of compounds. In this study, we evaluated the antinociceptive effects of the JNK inhibitor SU 3327 (0.3-30 mg/kg) in the formalin pain model with an emphasis on the sex-specific actions of this compound. In wild-type C57BL6J mice, SU 3327 produced strong antinociceptive effects in the formalin pain model which were mediated by CB₂ receptors in females, and both CB₁ and CB₂ receptors in males. SU 3327 at a dose of 10 mg/kg produced antinociception, hypothermia, motor impairment, and hypolocomotion to a similar extent in both males and females. The antinociceptive effects of SU 3327 were more potent in males at lower doses (1 and 3 mg/kg), while females were more sensitive to the hypothermic, and motor-suppression effects at lower (3 mg/kg) doses versus males. Analysis of spinal cords, using qPCR following SU 3327 administration in the formalin test, revealed changes in cannabinoid, tolerance and inflammatory markers in females only, and only in the high (10-30 mg/kg) dose conditions. Indeed, females showed an increase in mRNA levels of cannabinoid (CB₂), but a decrease in tolerance (β-arrestin 1) and inflammatory (TNF-α, IL-1β, IL-6)-associated markers. The differences between males and females, in this study, support sex as an important factor in nociception and antinociceptive responses mediated by JNK and the endocannabinoid system.

Sex Differences in Tolerance to Delta-9-Tetrahydrocannabinol in Mice With Cisplatin-Evoked Chronic Neuropathic Pain

Tolerance to the pain-relieving effects of cannabinoids limits the therapeutic potential of these drugs in patients with chronic pain. Recent preclinical research with rodents and clinical studies in humans has suggested important differences between males and females in the development of tolerance to cannabinoids. Our previous work found that male mice expressing a desensitization resistant form (S426A/S430A) of the type 1 cannabinoid receptor (CB₁R) show delayed tolerance and increased sensitivity to the antinociceptive effects of delta-9-tetrahydrocannabinol (∆⁹-THC). Sex differences in tolerance have been reported in rodent models with females acquiring tolerance to ∆⁹-THC faster than males. However, it remains unknown whether the S426A/S430A mutation alters analgesic tolerance to ∆⁹-THC in mice with chemotherapy-evoked chronic neuropathic pain, and also whether this tolerance might be different between males and females. Male and female S426A/S430A mutant and wild-type littermates were made neuropathic using four once-weekly injections of 5 mg/kg cisplatin and subsequently assessed for tolerance to the anti-allodynic effects of 6 and/or 10 mg/kg ∆⁹-THC. Females acquired tolerance to the anti-allodynic effects of both 6 and 10 mg/kg ∆⁹-THC faster than males. In contrast, the S426A/S430A mutation did not alter tolerance to ∆⁹-THC in either male or female mice. The anti-allodynic effects of ∆⁹-THC were blocked following pretreatment with the CB₁R antagonist, rimonabant, and partially blocked following pretreatment with the CB₂R inverse agonist, SR144528. Our results show that disruption of the GRK/β-arrestin-2 pathway of desensitization did not affect sensitivity and/or tolerance to ∆⁹-THC in a chronic pain model of neuropathy.

Long-lasting analgesia via targeted in situ repression of NaV1.7 in mice

Current treatments for chronic pain rely largely on opioids despite their substantial side effects and risk of addiction. Genetic studies have identified in humans key targets pivotal to nociceptive processing. In particular, a hereditary loss-of-function mutation in NaV1.7, a sodium channel protein associated with signaling in nociceptive sensory afferents, leads to insensitivity to pain without other neurodevelopmental alterations. However, the high sequence and structural similarity between NaV subtypes has frustrated efforts to develop selective inhibitors. Here, we investigated targeted epigenetic repression of NaV1.7 in primary afferents via epigenome engineering approaches based on clustered regularly interspaced short palindromic repeats (CRISPR)-dCas9 and zinc finger proteins at the spinal level as a potential treatment for chronic pain. Toward this end, we first optimized the efficiency of NaV1.7 repression in vitro in Neuro2A cells and then, by the lumbar intrathecal route, delivered both epigenome engineering platforms via adeno-associated viruses (AAVs) to assess their effects in three mouse models of pain: carrageenan-induced inflammatory pain, paclitaxel-induced neuropathic pain, and BzATP-induced pain. Our results show effective repression of NaV1.7 in lumbar dorsal root ganglia, reduced thermal hyperalgesia in the inflammatory state, decreased tactile allodynia in the neuropathic state, and no changes in normal motor function in mice. We anticipate that this long-lasting analgesia via targeted in vivo epigenetic repression of NaV1.7 methodology we dub pain LATER, might have therapeutic potential in management of persistent pain states.

Neuroinflammatory Process Involved in Different Preclinical Models of Chemotherapy-Induced Peripheral Neuropathy

Peripheral neuropathies are characterized by nerves damage and axonal loss, and they could be classified in hereditary or acquired forms. Acquired peripheral neuropathies are associated with several causes, including toxic agent exposure, among which the antineoplastic compounds are responsible for the so called Chemotherapy-Induced Peripheral Neuropathy (CIPN). Several clinical features are related to the use of anticancer drugs which exert their action by affecting different mechanisms and structures of the peripheral nervous system: the axons (axonopathy) or the dorsal root ganglia (DRG) neurons cell body (neuronopathy/ganglionopathy). In addition, antineoplastic treatments may affect the blood brain barrier integrity, leading to cognitive impairment that may be severe and long-lasting. CIPN may affect patient quality of life leading to modification or discontinuation of the anticancer therapy. Although the mechanisms of the damage are not completely understood, several hypotheses have been proposed, among which neuroinflammation is now emerging to be relevant in CIPN pathophysiology. In this review, we consider different aspects of neuro-immune interactions in several CIPN preclinical studies which suggest a critical connection between chemotherapeutic agents and neurotoxicity. The features of the neuroinflammatory processes may be different depending on the type of drug (platinum derivatives, taxanes, vinca alkaloids and proteasome inhibitors). In particular, recent studies have demonstrated an involvement of the immune response (both innate and adaptive) and the stimulation and secretion of mediators (cytokines and chemokines) that may be responsible for the painful symptoms, whereas glial cells such as satellite and Schwann cells might contribute to the maintenance of the neuroinflammatory process in DRG and axons respectively. Moreover, neuroinflammatory components have also been shown in the spinal cord with microglia and astrocytes playing an important role in CIPN development. Taking together, better understanding of these aspects would permit the development of possible strategies in order to improve the management of CIPN.

Renoprotective Effects of a New Free Radical Scavenger, XH-003, against Cisplatin-Induced Nephrotoxicity

Acute renal injury has an incidence of 25%–30% in patients with tumors who are treated with cisplatin and in patients for whom no specific drugs are available for treatment. Amifostine is the only FDA-approved chemoprotective drug; however, its clinical application is limited because of side effects. The small-molecule antioxidant XH-003, an acute radiation syndrome- (ARS-) protective drug independently developed in our laboratory, with 100% intellectual property rights, overcomes the side effects of amifostine but retains its high efficacy. In this study, XH-003 showed a chemoprotective effect similar to that of amifostine. A mechanistic study showed that XH-003 could significantly reduce cisplatin-induced increases in serum creatinine and urea nitrogen, increase the activity of antioxidant enzymes (SOD, CAT, and GSH-Px), reduce oxidative stress and tissue inflammation, and alleviate renal tissue damage by blocking the activity of the mitochondrial apoptosis pathway. Most importantly, XH-003 could reduce the accumulation of cisplatin in renal tissue by regulating the expression of proteins involved in cisplatin uptake and excretion, such as organic cation transporter 2 and MRP2. Moreover, in an in vivo xenotransplantation model, XH-003 did not interfere with the antitumor effect of cisplatin. These data provide strong evidence that the ARS-protective agent has a great potential for protecting against chemotherapy-induced toxicity. Thus, XH-003 can be considered in antitumor therapy.

A Higher Frequency Administration of the Nontoxic Cycloartane-Type Triterpene Argentatin A Improved Its Anti-Tumor Activity

Parthenium argentatum (Gray), commonly known as guayule, has been used to obtain natural rubber since the beginning of the 20th century. Additionally, the so called "resin" is a waste product derived from the industrial process. The cycloartane-type triterpene Argentatin A (AA) is one of the main constituents of the industrial waste resin. In this study we evaluated the AA anticancer activity both in vitro and in vivo in the HCT116 colon cancer cells. The apoptosis promotion of AA was assessed by the annexin V/propidium iodide (PI) assay. The senescence was evaluated for SA-β-galactosidase, and PCNA was used as a marker of proliferation. Its antitumor activity was evaluated using a xenograft mouse model. The results indicated that AA-induced apoptosis in HCT-116 cells and was positively stained for SA-β-galactosidase. In the xenografted mice test, the administration of AA at the dose of 250 mg/kg three times a week for 21 days reduced tumor growth by 78.1%. A comparable tumor reduction was achieved with cisplatin at the dose of 2 mg/kg administered three times a week for 21 days. However, nude mice treated with AA did not lose weight, as they did remarkably when treated with cisplatin. Furthermore, the animals treated with AA showed similar blood profiles as the healthy control group. These data indicate the low toxicity of AA compared to that shown by cisplatin.

Cucurbitacin B and cisplatin induce the cell death pathways in MB49 mouse bladder cancer model

IMPACT STATEMENT

Alternative agents that will increase the effectiveness of cisplatin, which are widely used in the advanced stage and metastatic bladder cancer, are being investigated. In previous studies, Cucurbitacin B (CuB), which is a natural compound from the Cucurbitaceae family has been shown to inhibit the proliferation of tumor cells and create synergistic effects with cisplatin. In this study, we investigated the synergistic effect of CuB with cisplatin for the first time in bladder cancer in vitro and in vivo models. Our findings showed that CuB treatment with cisplatin reduced cell proliferation, and reduced tumor development through activating apoptosis and autophagy via PI3K/AKT/mTOR signaling pathway. Our results showed that CuB may be a new agent that can support conventional treatment in bladder cancer. Our study is important in terms of enlightening new pathways and developing new treatment methods in the treatment of bladder cancer.

Anticancer Activities of the Quinone-Methide Triterpenes Maytenin and 22-β-hydroxymaytenin Obtained from Cultivated Maytenus ilicifolia Roots Associated with Down-Regulation of miRNA-27a and miR-20a/miR-17-5p

Natural triterpenes exhibit a wide range of biological activities. Since this group of secondary metabolites is structurally diverse, effects may vary due to distinct biochemical interactions within biological systems. In this work, we investigated the anticancer-related activities of the quinone-methide triterpene maytenin and its derivative compound 22-β-hydroxymaytenin, obtained from Maytenus ilicifolia roots cultivated in vitro. Their antiproliferative and pro-apoptotic activities were evaluated in monolayer and three-dimensional cultures of immortalized cell lines. Additionally, we investigated the toxicity of maytenin in SCID mice harboring tumors derived from a squamous cell carcinoma cell line. Both isolated molecules presented pronounced pro-apoptotic activities in four cell lines derived from head and neck squamous cell carcinomas, including a metastasis-derived cell line. The molecules also induced reactive oxygen species (ROS) and down-regulated microRNA-27a and microRNA-20a/miR-17-5p, corroborating with the literature data for triterpenoids. Intraperitoneal administration of maytenin to tumor-bearing mice did not lead to pronounced histopathological changes in kidney tissue, suggesting low nephrotoxicity. The wide-ranging activity of maytenin and 22-β-hydroxymaytenin in head and neck cancer cells indicates that these molecules should be further explored in plant biochemistry and biotechnology for therapeutic applications.

Insights into platinum-induced peripheral neuropathy-current perspective

Cancer is a global health problem that is often successfully addressed by therapy, with cancer survivors increasing in numbers and living longer world around. Although new cancer treatment options are continuously explored, platinum based chemotherapy agents remain in use due to their efficiency and availability. Unfortunately, all cancer therapies affect normal tissues as well as cancer, and more than 40 specific side effects of platinum based drugs documented so far decrease the quality of life of cancer survivors. Chemotherapy-induced peripheral neuropathy is a frequent side effects of platinum-based chemotherapy agents. This cluster of complications is often so debilitating that patients occasionally have to discontinue the therapy. Sensory neurons of dorsal root ganglia are at the core of chemotherapy-induced peripheral neuropathy symptoms. In these postmitotic cells, DNA damage caused by platinum chemotherapy interferes with normal functioning. Accumulation of DNA-platinum adducts correlates with neurotoxic severity and development of sensation of pain. While biochemistry of DNA-platinum adducts is the same in all cell types, molecular mechanisms affected by DNA-platinum adducts are different in cancer cells and non-dividing cells. This review aims to raise awareness about platinum associated chemotherapy-induced peripheral neuropathy as a medical problem that has remained unexplained for decades. We emphasize the complexity of this condition both from clinical and mechanistical point of view and focus on recent findings about chemotherapy-induced peripheral neuropathy in in vitro and in vivo model systems. Finally, we summarize current perspectives about clinical approaches for chemotherapy-induced peripheral neuropathy treatment.

c-Jun N terminal kinase signaling pathways mediate cannabinoid tolerance in an agonist-specific manner

Tolerance to the antinociceptive effects of cannabinoids represents a significant limitation to their clinical use in managing chronic pain. Tolerance likely results from desensitization and down-regulation of the cannabinoid type 1 receptor (CB₁R), with CB₁R desensitization occurring via phosphorylation of CB₁Rs by a G protein-coupled receptor kinase and subsequent association with an arrestin protein. Previous studies have shown that (1) desensitization-resistant S426A/S430A mice exhibit a modest delay in tolerance for Δ⁹-THC and (-)-CP55,940 but a more pronounced disruption in tolerance for WIN 55,212-2 and (2) that c-Jun N-terminal kinase (JNK) signaling may selectively mediate antinociceptive tolerance to morphine compared to other opioid analgesics. In the current study, we found that pretreatment with the JNK inhibitor SP600125 (3 mg/kg) attenuates tolerance to the antinociceptive in the formalin test and to the anti-allodynic effects of Δ⁹-THC (6 mg/kg) in cisplatin-evoked neuropathic pain using wild-type mice. We also find that SP600125 causes an especially robust reduction in tolerance to the antinociceptive effects of Δ⁹-THC (30 mg/kg), but not WIN 55,212-2 (10 mg/kg) in the tail-flick assay using S426A/S430A mice. Interestingly, SP600125 pretreatment accelerated tolerance to the antinociceptive and anti-allodynic effects of (-)-CP55,940 (0.3 mg/kg) in mice with acute and neuropathic pain. These results demonstrate that inhibition of JNK signaling pathways delay tolerance to Δ⁹-THC, but not to CP55,940 or WIN55,212-2, demonstrating that the mechanisms of cannabinoid tolerance are agonist-specific.

Protective Role of Natural Products in Cisplatin-Induced Nephrotoxicity

Cisplatin is a widely used antineoplastic agent for the treatment of metastatic tumors, advanced bladder cancer and many other solid tumors. However, at higher doses, toxicities such as nephrotoxicity may appear. Cisplatin leads to DNA damage and subsequently renal cell death. Besides that, oxidative stress is also implicated as one of the main causes of nephrotoxicity. Several studies showed that numerous natural products: ginseng, curcumin, licorice, honey and pomegranate were able to reduce the oxidative stress by restoring the levels of antioxidant enzymes and also at the same time act as an anti-inflammatory agent. Furthermore, pre-treatment with vitamin supplementation, such as vitamin C, E and riboflavin markedly decreased serum urea and increased the levels of antioxidant enzymes in the kidney even after cisplatin induction in cancer patients. These natural products possess potent antioxidant and anti-inflammatory medicinal properties, and they can be safely used as a supplementary regime or combination therapy against cisplatin-induced nephrotoxicity. The present review focused on the protective role of a few natural products which is widely used in folk medicines in cisplatin-induced nephrotoxicity.

Front and hind paw differential analgesic effects of amitriptyline, gabapentin, ibuprofen, and URB937 on mechanical and cold sensitivity in cisplatin-induced neuropathy

Cisplatin is a widely used platinum-derived antineoplastic agent that frequently results in peripheral neuropathy. Therapeutic strategies for neuropathic pain are limited and characterized by variable efficacy and severe adverse effects. Clinical translation of novel analgesics has proven difficult with many agents demonstrating preclinical efficacy failing in clinical trials. Preclinical studies frequently assess pain behaviors in the hind paws; however, the front paws have a greater degree of the fine sensorimotor functions characteristically damaged by chemotherapy-induced neuropathy. This is the first study to assess pain responses in the front paws. Here, we test the hypothesis that mouse front paws exhibit pain-related alterations in mechanical and thermal (cold) sensitivity in a murine model of cisplatin-induced neuropathy and that pharmacological treatment with amitriptyline, gabapentin, ibuprofen, and URB937 normalize pain behaviors in the front and hind paws. Cold (acetone withdrawal latencies) and mechanical (von Frey withdrawal thresholds) sensitivity were significantly increased and decreased respectively in both the front and the hind paws following initiation of weekly systemic (intraperitoneal) cisplatin injections (5 mg/kg). For the hind paws, systemic administration of amitriptyline (30 mg/kg), gabapentin (100 mg/kg), ibuprofen (0–10 mg/kg), or URB937 (0–10 mg/kg) resulted in a decrease in acetone withdrawal latencies and increase in von Frey withdrawal thresholds with return to normal values at the highest doses tested. For the front paws, return to baseline values for the highest doses was found for cold allodynia but not mechanical allodynia, where the highest doses failed to return to baseline values. These results indicate that mouse front paws exhibit pain-related changes in cisplatin-induced neuropathy and that drug effects can vary based on testing stimulus and location. This suggests that front paw responses across multiple modalities provide reliable and accurate information about pain-related drug effects. Future studies should be aimed at elucidating the mechanisms underlying these differential effects.

Pioglitazone, a PPARγ agonist, reduces cisplatin-evoked neuropathic pain by protecting against oxidative stress

Painful peripheral neuropathy is a dose-limiting side effect of cisplatin treatment. Using a murine model of cisplatin-induced hyperalgesia, we determined whether a PPARγ synthetic agonist, pioglitazone, attenuated the development of neuropathic pain and identified underlying mechanisms. Cisplatin produced mechanical and cold hyperalgesia and decreased electrical thresholds of Aδ and C fibers, which were attenuated by coadministration of pioglitazone (10 mg/kg, intraperitoneally [i.p.]) with cisplatin. Antihyperalgesic effects of pioglitazone were blocked by the PPARγ antagonist T0070907 (10 mg/kg, i.p.). We hypothesized that the ability of pioglitazone to reduce the accumulation of reactive oxygen species (ROS) in dorsal root ganglion (DRG) neurons contributed to its antihyperalgesic activity. Effects of cisplatin and pioglitazone on somatosensory neurons were studied on dissociated mouse DRG neurons after 24 hours in vitro. Incubation of DRG neurons with cisplatin (13 µM) for 24 hours increased the occurrence of depolarization-evoked calcium transients, and these were normalized by coincubation with pioglitazone (10 µM). Oxidative stress in DRG neurons was considered a significant contributor to cisplatin-evoked hyperalgesia because a ROS scavenger attenuated hyperalgesia and normalized the evoked calcium responses when cotreated with cisplatin. Pioglitazone increased the expression and activity of ROS-reducing enzymes in DRG and normalized cisplatin-evoked changes in oxidative stress and labeling of mitochondria with the dye MitoTracker Deep Red, indicating that the antihyperalgesic effects of pioglitazone were attributed to its antioxidant properties in DRG neurons. These data demonstrate clear benefits of broadening the use of the antidiabetic drug pioglitazone, or other PPARγ agonists, to minimize the development of cisplatin-induced painful neuropathy.

The Evaluation of the Effects of N-Acetylcysteine on Cisplatin-Induced Alterations in Exploratory Activity in Elevated Plus Maze Test in Rats

The aim of this study was to evaluate the potential beneficial effect of N-acetylcysteine (NAC) on cisplatin-induced alterations in anxiety levels in rats, by means of parameters of the exploratory activity obtained in the elevated plus maze (EPM) test. Animals were divided into four groups: control group, cisplatin group (7.5 mg/kg/weekly of cisplatin), N-acetylcysteine group (500 mg/kg/weekly of NAC), and cisplatin plus N-acetylcysteine group (7.5 mg/kg/weekly of cisplatin, and 500 mg/kg/weekly of NAC). After two weeks of treatment, exploratory activity (estimated by means of the number of rearings, head-dippings and the number of total exploratory activity episodes) was significantly reduced in cisplatin group comparing to control values. Although NAC induced no alterations in exploratory activity when applied alone, simultaneous administration with cisplatin resulted in significant attenuation of cisplatin-induced decline in exploratory activity. The exploratory activity gradually decreased in time-dependent manner during five minutes of EPM test in all groups. The results of this study confirmed clear beneficial effect of NAC supplementation against cisplatin- induced neurotoxicity in rats. Antioxidative properties of NAC were manifested through restoration of exploratory activity, confirming that NAC administration can attenuate anxiogenic effect of cisplatin therapy. Those results could recommend NAC supplementation as a potential protection against cisplatin-induced neurotoxicity.

Tolerance to WIN55,212-2 is delayed in desensitization-resistant S426A/S430A mice

Tolerance to cannabinoid agonists can develop through desensitization of the cannabinoid receptor 1 (CB1) following prolonged administration. Desensitization results from phosphorylation of CB1 by a G protein-coupled receptor kinase (GRK), and subsequent association of the receptor with arrestin. Mice expressing a mutant form of CB1, in which the serine residues at two putative phosphorylation sites necessary for desensitization have been replaced by non-phosphorylatable alanines (S426A/S430A), display reduced tolerance to Δ9-tetrahydrocannabinol (Δ9-THC). Tolerance to the antinociceptive effects of WIN55,212-2 was delayed in S426A/S430A mutants using the tail-flick and formalin tests. However, tolerance to the antinociceptive effects of once daily CP55,940 injections was not significantly delayed in S426A/S430A mutant mice using either of these tests. Interestingly, the dose response curve shifts for the hypothermic and antinociceptive effects of CP55,940 that were induced by chronic treatment with this agonist in wild-type mice were blocked in S426A/S430A mutant mice. Assessment of mechanical allodynia in mice exhibiting chronic cisplatin-evoked neuropathic pain found that tolerance to the anti-allodynic effects WIN55,212-2 but not CP55,940 was delayed in S426A/S430A mice compared to wild-type littermates. Despite these deficits in tolerance, S426A/S430A mutant mice eventually developed tolerance to both WIN55,212-2 and CP55,940 for all pain assays that were examined, suggesting that other mechanisms likely contribute to tolerance for these cannabinoid agonists. These findings suggest that GRK- and βarrestin2-mediated desensitization of CB1 may strongly contribute to the rate of tolerance to the antinociceptive effects of WIN55,212-2, and raises the possibility of agonist-specific mechanisms of cannabinoid tolerance.

The effect of thiamine and its metabolites on peripheral neuropathic pain induced by cisplatin in rats

Thiamine pyrophosphate (TPP) is the active metabolite of thiamine. This study aimed to investigate the effects of thiamine and TPP on cisplatin-induced peripheral neuropathic pain (PNP). Male albino Wistar type Rattus norvegicus were divided into six groups (n=6) that received 2 mg/kg cisplatin (CIS), 25 mg/kg thiamine (TM), 2 mg/kg cisplatin+25 mg/kg thiamine (CTM), 25 mg/kg TPP (TPP), 2 mg/kg cisplatin+25 mg/kg TPP (CTPP), or distilled water (healthy group; HG) for 8 days intraperitoneally. Analgesic effect was measured with a Basile Algesimeter. IL-1β, malondialdehyde (MDA), total glutathione (tGSH), thiamine, and TPP were determined in blood samples. Histopathological examinations were performed on removed sciatic nerves. The percent analgesic effects of the CTM and CTPP groups were calculated to be 21.3% and 82.9%, respectively. Increased production of IL-1β and MDA by cisplatin was inhibited by TPP, while it was not inhibited by thiamine. Conversion of thiamine to TPP significantly decreased in the CIS group. Histopathological and biochemical investigations demonstrated that hyperalgesia and sciatic nerve damage developed in the CIS and CTM groups with low TPP levels. These results indicate that cisplatin inhibits the formation of TPP from thiamine, leading to severe PNP. This finding suggests that TPP may be more beneficial than thiamine for the treatment of cisplatin-induced PNP.

Paclitaxel-induced hypothermia and hypoperfusion increase breast cancer metastasis and angiogenesis in mice

Housing temperature has been shown to influence thermoregulation and behavior of preclinical cancer models; and anti-cancer drugs typically reduce peripheral blood flow and body temperature. In the present study, the effects of paclitaxel (PTX)-induced reduction of body temperature and peripheral blood flow on metastatic 4T1 breast cancer was investigated in a mouse model and the modification of these effects by thermoneutral temperature was also assessed. A single dose of PTX decreased the body temperature and peripheral blood flow in mice housed at a standard temperature (23°C). Furthermore, although lung metastasis and angiogenesis of inoculated 4T1 cells increased in mice pretreated with PTX, mice housed at a thermoneutral temperature (30°C) could compensate their body temperature and peripheral blood flow compared with control mice, and also suppressed 4T1 angiogenesis and metastasis to lung. The present results imply that maintenance of body temperature or efficient energy supply for thermogenesis may prevent tumor relapse or metastasis after chemotherapy.

Masticadienonic and 3&#945;-OH Masticadienoic Acids Induce Apoptosis and Inhibit Cell Proliferation and Tumor Growth in Prostate Cancer Xenografts in Vivo

The triterpenes have been constituted as a group of interesting molecules as possible antitumor agents. Despite several of them not presenting a potent cytotoxic activity in vitro against cancer cells, in vivo in xenotransplant tumors studies, they show promising results. Based on the above considerations, we investigated the antitumor activity of both masticadienonic (MDA) and 3&#945;-OH masticadienoic (3&#945;-OH MDA) acids in a mouse prostate cancer xenograft model. Immunohistochemical assays were used to evaluate the decrease in the expression of the Proliferating Cell Nuclear Antigen (PCNA) and the Ki-67 induced by MDA and 3&#945;-OH MDA. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay was performed to demonstrate the fragmentation of DNA. Our results showed that the two triterpenes inhibited tumor growth, had anti-proliferative effect in vivo and induced cell death by apoptosis. Collectively, our data suggested that the antitumor mechanism of MDA and 3&#945;-OH MDA involves several molecular targets related to cell proliferation and apoptosis.

The use of antioxidant agents for chemotherapy-induced peripheral neuropathy treatment in animal models

Antineoplastic drugs such as cisplatin, oxaliplatin, paclitaxel and vincristin are widely used in the treatment of several solid and blood tumours. However, the severity of peripheral neuropathy caused by these agents can affect the patient's quality of life. The major symptoms of chemotherapy-induced peripheral neuropathy (CIPN) involve: sensory loss, paresthesia, dysesthaesia, numbness, tingling, temperature sensitivity, allodynia and hyperalgesia, in a "stocking and glove" distribution. Why many different chemotherapeutic agents result in similar neuropathy profiles is unclear. Many drug classes such as antidepressants, anticonvulsants, antispastic agents and others have been used in clinical practice, but there is no scientific evidence to prove their effectiveness. But drugs as the antioxidant have shown a protective effect against free radical damage. In order to find out a successful treatment for CIPN, animal studies (ie pharmacological and mechanical tests and histopathological immunohistochemical analyses) have been developed to try to determinate the action of the antioxidant agents. This review provides an overview of the major antioxidant agents recently investigated to treat CIPN and the animal models used for this purpose.

Lifestyle-Related Factors in the Self-Management of Chemotherapy-Induced Peripheral Neuropathy in Colorectal Cancer: A Systematic Review

Background. Chemotherapy-induced peripheral neuropathy (CIPN) is a common adverse effect of chemotherapy treatment in colorectal cancer (CRC), negatively affecting the daily functioning and quality of life of CRC patients. Currently, there are no established treatments to prevent or reduce CIPN. The purpose of this systematic review was to identify lifestyle-related factors that can aid in preventing or reducing CIPN, as such factors may promote self-management options for CRC patients suffering from CIPN. Methods. A literature search was conducted through PubMed, Embase, and Google Scholar. Original research articles investigating oxaliplatin-related CIPN in CRC were eligible for inclusion. Results. In total, 22 articles were included, which suggested that dietary supplements, such as antioxidants and herbal extracts, as well as physical exercise and complementary therapies, such as acupuncture, may have beneficial effects on preventing or reducing CIPN symptoms. However, many of the reviewed articles presented various limitations, including small sample sizes and heterogeneity in study design and measurements of CIPN. Conclusions. No strong conclusions can be drawn regarding the role of lifestyle-related factors in the management of CIPN in CRC patients. Certain dietary supplements and physical exercise may be beneficial for the management of CIPN, but further research is warranted.

Endogenous Opiates and Behavior: 2015

This paper is the thirty-eighth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2015 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

Binge Ethanol Consumption Increases Inflammatory Pain Responses and Mechanical and Cold Sensitivity: Tigecycline Treatment Efficacy Shows Sex Differences

Background

Physicians have long reported that patients with chronic pain show higher tendencies for alcohol use disorder (AUD), and AUD patients appear to have higher pain sensitivities. The goal of this study was to test 2 hypotheses: (i) binge alcohol consumption increases inflammatory pain and mechanical and cold sensitivities; and (ii) tigecycline is an effective treatment for alcohol‐mediated‐increased pain behaviors and sensitivities. Both female and male mice were used to test the additional hypothesis that important sex differences in the ethanol (EtOH)‐related traits would be seen.

Methods

“Drinking in the Dark” (DID) alcohol consuming and nondrinking control, female and male, adult C57BL/6J mice were evaluated for inflammatory pain behaviors and for the presence of mechanical and cold sensitivities. Inflammatory pain was produced by intraplantar injection of formalin (10 μl, 2.5% in saline). For cold sensation, a 20 μl acetone drop was used. Mechanical withdrawal threshold was measured by an electronic von Frey anesthesiometer. Efficacy of tigecycline (80 mg/kg i.p.) to reduce DID‐related pain responses and sensitivity was tested.

Results

DID EtOH consumption increased inflammatory pain behavior, while it also produced sustained mechanical and cold sensitivities in both females and males. Tigecycline produced antinociceptive effects in males; a pro‐nociceptive effect was seen in females in the formalin test. Likewise, the drug reduced both mechanical and cold sensitivities in males, but females showed an increase in sensitivity in both tests.

Conclusions

Our results demonstrated that binge drinking increases pain, touch, and thermal sensations in both sexes. In addition, we have identified sex‐specific effects of tigecycline on inflammatory pain, as well as mechanical and cold sensitivities. The development of tigecycline as an AUD pharmacotherapy may need consideration of its pro‐nociceptive action in females. Further studies are needed to investigate the mechanism underlying the sex‐specific differences in nociception.

Prevention of chemotherapy-induced peripheral neuropathy by the small-molecule inhibitor pifithrin-μ

Chemotherapy-induced peripheral neuropathy (CIPN) is a common side effect of cancer treatment. It is the most frequent cause of dose reduction or treatment discontinuation in patients treated for cancer with commonly used drugs including taxanes and platinum-based compounds. No FDA-approved treatments for CIPN are available. In rodents, CIPN is represented by peripheral mechanical allodynia in association with retraction of intraepidermal nerve fibers. The mechanism of chemotherapy-induced neurotoxicity is unclear, but it has been established that mitochondrial dysfunction is an important component of the dysregulation in peripheral sensory neurons. We have shown earlier that inhibition of mitochondrial p53 accumulation with the small compound pifithrin-μ (PFT-μ) prevents cerebral neuronal death in a rodent model of hypoxic-ischemic brain damage. We now explore whether PFT-μ is capable of preventing neuronal mitochondrial damage and CIPN in mice. We demonstrate for the first time that PFT-μ prevents both paclitaxel- and cisplatin-induced mechanical allodynia. Electron microscopic analysis of peripheral sensory nerves revealed that PFT-μ secured mitochondrial integrity in paclitaxel-treated mice. In addition, PFT-μ administration protects against chemotherapy-induced loss of intraepidermal nerve fibers in the paw. To determine whether neuroprotective treatment with PFT-μ would interfere with the antitumor effects of chemotherapy, ovarian tumor cells were cultured in vitro with PFT-μ and paclitaxel. Pifithrin-μ does not inhibit tumor cell death but even enhances paclitaxel-induced tumor cell death. These data are the first to identify PFT-μ as a potential therapeutic strategy for prevention of CIPN to combat one of the most devastating side effects of chemotherapy.

Tolerance to the antinociceptive effects of chronic morphine requires c-Jun N-terminal kinase

BACKGROUND

Morphine and fentanyl are opioid analgesics in wide clinical use that act through the μ-opioid receptor (MOR). However, one limitation of their long-term effectiveness is the development of tolerance. Receptor desensitization has been proposed as a putative mechanism driving tolerance to G protein-coupled receptor (GPCR) agonists. Recent studies have found that tolerance to morphine is mediated by the c-Jun N-terminal Kinase (JNK) signaling pathway. The goal of the present study was to test the hypotheses that: 1) JNK inhibition will be antinociceptive on its own; 2) JNK inhibition will augment morphine antinociception and; 3) JNK mediates chronic tolerance for the antinociceptive effects of morphine using acute (hotplate and tail-flick), inflammatory (10 μl of formalin 2.5%) and chemotherapy (cisplatin 5 mg/kg ip once weekly)-induced neuropathic pain assays.

RESULTS

We found that JNK inhibition by SP600125 (3 mg/kg) produces a greater antinociceptive effect than morphine (6 mg/kg) alone in the formalin test. Moreover, co-administration of morphine (6 mg/kg) with SP600125 (3 mg/kg) produced a sub-additive antinociceptive effect in the formalin test. We also show that pre-treatment with SP600125 (3 or 10 mg/kg), attenuates tolerance to the antinociceptive effects of morphine (10 mg/kg), but not fentanyl (0.3 mg/kg), in the tail-flick and hotplate tests. Pre-treatment with SP600125 also attenuates tolerance to the hypothermic effects of both morphine and fentanyl. We also examined the role of JNK in morphine tolerance in a cisplatin-induced model of neuropathic pain. Interestingly, treatment with SP600125 (3 mg/kg) alone attenuated mechanical and cold allodynia in a chemotherapy-induced pain model using cisplatin. Strikingly, SP600125 (3 mg/kg) pre-treatment prolonged the anti-allodynic effect of morphine by several days (5 and 7 days for mechanical and cold, respectively).

CONCLUSIONS

These results demonstrate that JNK signaling plays a crucial role in mediating antinociception as well as chronic tolerance to the antinociceptive effects of morphine in acute, inflammatory, and neuropathic pain states. Thus, inhibition of JNK signaling pathway, via SP600125, represents an efficacious pharmacological approach to delay tolerance to the antinociceptive effects of chronic morphine in diverse pain models.